Room temperature photoluminescence of mixed titanium-manganese oxides

Titanium-manganese mixed oxides TiO2/MnOx (TMO) were prepared by chemical precipitation of manganese hydroxide on pure nanocrystalline rutile TiO2 particles with subsequent thermal treatment at different temperatures. The morphology, structural and optical properties of TMO samples were investigated using standard XRD, SEM, EDS, XRF, TGA, FT-Raman and UV-vis absorption spectroscopic techniques. The photoluminescence (PL) in TMO was excited by the UV laser pulses (337.1 nm). All measurements were carried out at room temperature. Examination of PL spectra revealed that they are strongly dependent on the phase composition and Mn concentration in TMO compounds. The quenching of the PL is connected with the oxygen vacancies in the TMO structure, in particular, the intensity lowering for the near band edge emission at 3.06 eV (405 nm) and the free exciton emission at 2.92 eV (424 nm) is interpreted by the non-radiative Auger recombination. The relative increase and decrease in the ratio of PL intensities for UV and visible bands with increasing Mn content (from 9 to 16 at%) is explained by the concentration effects.